Vascular complications may occur after organ transplantation which can compromise the survival of the organ and, in some cases, the patient. Surgical resection of some organs such as the liver may introduce vascular complications to the remaining portion of the organ depending on the type and extent of the resection. This makes it important to monitor the surgically affected organs during the postsurgical period for the early detection of complications which may enable organ-saving intervention before the occurrence of irreversible tissue damage or total organ loss.
For example, monitoring of hepatic oxygenation is essential after liver transplantation and resection. Currently, the measurement of the liver enzymes and clotting factors via blood analysis is the only reliable way to monitor liver dysfunction. Changes in these laboratory values can be detected only after significant liver damage has already occurred and hence intervention usually takes place retrospectively. Also, these tests have no dynamic value since they indicate the liver condition only at the time when the blood sample is withdrawn.
Current organ monitoring technology offers probes that may require stitching or gluing to the tissue and therefore may not be easy to apply or remove especially if used inside the body, which has been a key limitation to wide acceptance in the medical field. Probe stitching to the surface of an organ may also disturb the local microvasculature, cause subcapsular hematoma, and interfere with the measurement of the probe. Following are some examples of commercially available organ and tissue monitoring technologies.
Thermodilution organ monitoring technology such as that produced by Hemedex Inc., MA, uses a catheter-like probe that is inserted into the organ to measure its perfusion using thermodilution. The tip of the catheter-like probe includes a thermistor that is heated to remain slightly above the tissue temperature. The local perfusion is estimated from the power used in heating the thermistor, which generally depends on the ability of the tissue to dissipate heat by both thermal conduction within the tissue and by thermal convection due to tissue blood flow. This organ-invasive probe may cause bleeding, subcapsular hematoma, and may require extra care during insertion to avoid the puncture of underlying vessels.
Doppler ultrasound graft monitoring technology such as that produced by Cook Vascular Inc., PA, uses a suturable cuff probe that is fitted around the vessels supplying the tissue to assess its blood flow using Doppler ultrasound. Post-monitoring, the cuff probe may be difficult to remove and may left permanently around the vessel.
Optical tissue monitoring technology such as that produced by Spectros Corporation, CA, uses button-like probes are stitched to the tissue to measure its oxygen saturation using reflectance spectroscopy (e.g. Stitching can complicate probe application and removal. Also, stitching may disturb the local microcirculation and introduces measurement errors.
Laser Doppler Flowmetry tissue monitoring technology such as that produced by Perimed A B, Sweden, uses button-like probes are stitched to the tissue to measure its blood perfusion using laser Doppler flowmetry. Again, stitching can complicate probe application and removal and disturb the local microcirculation thereby introducing measurement errors.
US Publication No. US 2004/0230118A1 with publication date Nov. 18, 2004 discloses a Jackson-Pratt (JP) surgical drain with embedded sensors for monitoring organs and tissues. One disadvantage of this configuration is the inability of the user to select the location of the sensors along the length of the drain. In addition, this configuration is constrained to a specific category of surgical drains having a shape and cross-section that can accommodate embedded sensors.
Surgical drains (or surgical wound drains, used interchangeably herein) are routinely used in and after many surgical procedures to drain the wound exudate out of the body. Some well-known examples of the surgical drains are the Jackson-Pratt (JP) drains (e.g. Jackson F E and Fleming P M, “Jackson-Pratt brain drain: use in general surgical conditions requiring drainage,” International Surgery, Vol. 57, No 8, page 658-659, 1972), and the flat drains (e.g. U.S. Pat. No. 4,317,452 and U.S. Pat. No. 4,257,422), and the Blake drains (e.g. U.S. Pat. Des. 288,962, U.S. Pat. No. 4,398,910, and U.S. Pat. No. 4,465,481). Surgical drains are generally used with a vacuum source to remove wound exudate postoperatively.